Performance for a WPF-based program that uses the layered windows feature may be less than expected in Windows Vista

For a Microsoft Windows XP and Windows Server 2003 version of this article, see 937106 .


Performance for a Windows Presentation Foundation (WPF)-based program may be less than expected in Windows Vista. For example, you may experience jittery animation, a low frame rate, or high CPU usage. This problem occurs if the program uses the layered windows feature. This feature is enabled if the value of the Windows.AllowsTransparency property is set to TRUE.


Service pack information

To resolve this problem, obtain the latest service pack for Windows Vista. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
935791 How to obtain the latest Windows Vista service pack

Update information

To resolve this problem, install one of the following updates, as appropriate for your situation.

Update for Windows Vista

Update for Windows Vista for x64-based Systems

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


No prerequisites are required.

Restart requirement

You must restart your computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.
Windows Vista, 32-bit versions
File nameFile versionFile sizeDateTimePlatform
Update.mumNot applicable2,01914-Jul-200711:43Not applicable
X86_e6a5b0032afc4b474bcdbe6b836b61e5_31bf3856ad364e35_6.0.6000.20640_none_10cd22566573d1e6.manifestNot applicable71214-Jul-200711:43Not applicable
X86_microsoft-windows-d..opwindowmanager-api_31bf3856ad364e35_6.0.6000.20640_none_de87011c5c14dc6a.manifestNot applicable8,24814-Jul-200711:46Not applicable
Windows Vista, 64-bit versions
File nameFile versionFile sizeDateTimePlatform
Amd64_e6a5b0032afc4b474bcdbe6b836b61e5_31bf3856ad364e35_6.0.6000.20640_none_6cebbdda1dd1431c.manifestNot applicable71414-Jul-200711:44Not applicable
Amd64_e8df770df4b5f7ff01707a48f97b632a_31bf3856ad364e35_6.0.6000.20640_none_5483415d32e22260.manifestNot applicable71614-Jul-200711:44Not applicable
Amd64_microsoft-windows-d..opwindowmanager-api_31bf3856ad364e35_6.0.6000.20640_none_3aa59ca014724da0.manifestNot applicable8,28214-Jul-200711:50Not applicable
Package_1_for_kb938660~31bf3856ad364e35~amd64~~ applicable1,81114-Jul-200711:44Not applicable
Package_2_for_kb938660~31bf3856ad364e35~amd64~~ applicable2,03014-Jul-200711:44Not applicable
Update.mumNot applicable2,01914-Jul-200711:43Not applicable


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. This problem was first corrected in Windows Vista Service Pack 1.

More Information

For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates